// The killring.
//
// Works like the killring in emacs and readline. The killring is cut and paste with a memory of
// previous cuts. It supports integration with the X clipboard.
#include <stdbool.h>
#include <stddef.h>
#include <algorithm>
#include <list>
#include <memory>
#include <string>

#include "common.h"
#include "env.h"
#include "exec.h"
#include "fallback.h"  // IWYU pragma: keep
#include "kill.h"
#include "path.h"

/** Kill ring */
typedef std::list<wcstring> kill_list_t;
static kill_list_t kill_list;

/// Contents of the X clipboard, at last time we checked it.
static wcstring cut_buffer;

/// Test if the xsel command is installed.  Since this is called often, cache the result.
static int has_xsel() {
    static signed char res = -1;
    if (res < 0) {
        res = !!path_get_path(L"xsel", NULL);
    }

    return res;
}

void kill_add(const wcstring &str) {
    ASSERT_IS_MAIN_THREAD();
    if (str.empty()) return;

    wcstring cmd;
    wcstring escaped_str;
    kill_list.push_front(str);

    // Check to see if user has set the FISH_CLIPBOARD_CMD variable, and, if so, use it instead of
    // checking the display, etc.
    //
    // I couldn't think of a safe way to allow overide of the echo command too, so, the command used
    // must accept the input via stdin.
    const env_var_t clipboard_wstr = env_get_string(L"FISH_CLIPBOARD_CMD");
    if (!clipboard_wstr.missing()) {
        escaped_str = escape(str.c_str(), ESCAPE_ALL);
        cmd.assign(L"echo -n ");
        cmd.append(escaped_str);
        cmd.append(clipboard_wstr);
    } else {
        // This is for sending the kill to the X copy-and-paste buffer.
        if (!has_xsel()) {
            return;
        }

        const env_var_t disp_wstr = env_get_string(L"DISPLAY");
        if (!disp_wstr.missing()) {
            escaped_str = escape(str.c_str(), ESCAPE_ALL);
            cmd.assign(L"echo -n ");
            cmd.append(escaped_str);
            cmd.append(L" | xsel -i -b");
        }
    }

    if (!cmd.empty()) {
        if (exec_subshell(cmd, false /* do not apply exit status */) == -1) {
            // Do nothing on failure.
        }
        cut_buffer = escaped_str;
    }
}

/// Remove first match for specified string from circular list.
static void kill_remove(const wcstring &s) {
    ASSERT_IS_MAIN_THREAD();
    kill_list_t::iterator iter = std::find(kill_list.begin(), kill_list.end(), s);
    if (iter != kill_list.end()) kill_list.erase(iter);
}

void kill_replace(const wcstring &old, const wcstring &newv) {
    kill_remove(old);
    kill_add(newv);
}

const wchar_t *kill_yank_rotate() {
    ASSERT_IS_MAIN_THREAD();
    // Move the first element to the end.
    if (kill_list.empty()) {
        return NULL;
    }
    kill_list.splice(kill_list.end(), kill_list, kill_list.begin());
    return kill_list.front().c_str();
}

/// Check the X clipboard. If it has been changed, add the new clipboard contents to the fish
/// killring.
static void kill_check_x_buffer() {
    if (!has_xsel()) return;

    const env_var_t disp = env_get_string(L"DISPLAY");
    if (!disp.missing()) {
        size_t i;
        wcstring cmd = L"xsel -t 500 -b";
        wcstring new_cut_buffer = L"";
        wcstring_list_t list;
        if (exec_subshell(cmd, list, false /* do not apply exit status */) != -1) {
            for (i = 0; i < list.size(); i++) {
                wcstring next_line = escape_string(list.at(i), 0);
                if (i > 0) new_cut_buffer += L"\\n";
                new_cut_buffer += next_line;
            }

            if (new_cut_buffer.size() > 0) {
                // The buffer is inserted with backslash escapes, since we don't really like tabs,
                // newlines, etc. anyway.
                if (cut_buffer != new_cut_buffer) {
                    cut_buffer = new_cut_buffer;
                    kill_list.push_front(new_cut_buffer);
                }
            }
        }
    }
}

const wchar_t *kill_yank() {
    kill_check_x_buffer();
    if (kill_list.empty()) {
        return L"";
    }
    return kill_list.front().c_str();
}

void kill_sanity_check() {}

void kill_init() {}

void kill_destroy() { cut_buffer.clear(); }
